Polling currently shows a 57/43 split in the Senate. If the dems can flip 3 more (along with an Obama/Biden victory) they would be able to run their agenda without opposition. Charlie Cook at The National Journal writes:
It might, just might, prompt the needed soul-searching at the GOP to flush the wingnuts and intolerant bigots from their midst and reconstitute a party based on sane, rational approaches to government. But I'm not going to bet on either one: a filibuster-proof majority or a less insane Republican party.
It seems farfetched that Republicans would lose Stevens, Sununu, Dole, Coleman, Smith, and Wicker, in addition to relinquishing the even more endangered open seats in Virginia, New Mexico, and Colorado, but a net loss of nine seats -- or eight if they topple Landrieu and keep Collins and McConnell in office -- is no longer implausible. In 2006, the odds against a six-seat Republican loss were equally strong, but it happened.
History shows, moreover, that close Senate races tend to break in the same direction, as they did two years ago.
The bottom line is that things have gotten worse for Senate Republicans over the past few weeks, so much worse that a magnitude of losses that seemed impossible just a few months ago now seems entirely possible.